On the Physical Geology of the Neighbourhood of Dublin. 151. 
across the end of this Upper Shale area, for which see Geological - 
Survey Explanations 102, page 62. 
The beds of this formation are in a synclinal basin, as is in- 
variably the case in Ireland, and the low hills which they form 
are hills of cireumdenudation. This brings us to the — 
Disturbance and Deiwudation which took place after the com- 
pletion of the whole of the Carboniferous formation, this being the 
third of which we have evidence in this district. Although in the 
western and west-central parts of the Carboniferous Limestone 
plain of Ireland the beds of that formation extend evenly and 
almost horizontally over considerable areas, yet elsewhere they 
have undergone disturbance and contortion, Such has been the 
case in the district with which we are now more immediately con- 
cerned, although by no means to the same extent as in the South 
of Ireland. In many places the beds have steep local dips. They 
are interestingly contorted at Loughshinny, three miles 8. of 
Skerries, evidently by horizontal compression, which has pro- 
duced even reversed faults. They are also strongly contorted ina 
quarry beside the bridge at Lucan and elsewhere. This disturbance 
being greater in the 8. and 8.E. of Ireland, has there produced a 
general system of cleavage pervading all the rocks from the lowest 
to the highest. The strike of this cleavage is in the 5S. about 
W.S.W. and E.N.E.; in the §.K. it gradually turns to about 5.8. W. 
and N.N,E., and itseems to die away a little outside the southern 
boundary of the map. This disturbance seems to have been (at 
least principally) effected at a time earlier than the Permian age; 
so that if, as seems most probable, no formations later than the 
Carboniferous were laid down in this district until the Drift 
period, the denuding agencies had nearly all the long period 
from that time to the present. in which-to work their will on the 
disturbed rocks. However this may be, they have very effec- 
tually availed themselves of the opportunities afforded them. - 
When -we consider that the Upper Shales just mentioned, and 
the overlying beds as far as they remain to us, are seen over 
the greater part of Ireland, to lie in synclinal basins, and that 
they are always remnant patches, whose limits are due to denu- 
dation and not to the dying-out of the beds, we reasonably 
conclude that these supra-Limestone beds once extended over a 
great part of the area now called Ireland, and that they have 
since been removed by denudation, The country around Dublin 
[ M 2 
